2AE9

Solution Structure of the theta subunit of DNA polymerase III from E. coli

Summary for 2AE9

• Entry DOI: 10.2210/pdb2ae9/pdb
• Descriptor: DNA polymerase III, theta subunit (1 entity in total)
• Functional Keywords: all helical, 3 helices, transferase
• Biological source: Escherichia coli
• Total number of polymer chains: 1
• Total formula weight: 8861.31

Authors

Mueller, G.A.,Kirby, T.W.,Derose, E.F.,Li, D.,Schaaper, R.M.,London, R.E. (deposition date: 2005-07-21, release date: 2005-10-18, Last modification date: 2024-05-22)

Primary citation

Mueller, G.A.,Kirby, T.W.,Derose, E.F.,Li, D.,Schaaper, R.M.,London, R.E.
Nuclear Magnetic Resonance Solution Structure of the Escherichia coli DNA Polymerase III {theta} Subunit.
J.Bacteriol., 187:7081-7089, 2005

PubMed Abstract: The catalytic core of Escherichia coli DNA polymerase III holoenzyme contains three subunits: alpha, epsilon, and theta. The alpha subunit contains the polymerase, and the epsilon subunit contains the exonucleolytic proofreading function. The small (8-kDa) theta subunit binds only to epsilon. Its function is not well understood, although it was shown to exert a small stabilizing effect on the epsilon proofreading function. In order to help elucidate its function, we undertook a determination of its solution structure. In aqueous solution, theta yielded poor-quality nuclear magnetic resonance spectra, presumably due to conformational exchange and/or protein aggregation. Based on our recently determined structure of the theta homolog from bacteriophage P1, named HOT, we constructed a homology model of theta. This model suggested that the unfavorable behavior of theta might arise from exposed hydrophobic residues, particularly toward the end of alpha-helix 3. In gel filtration studies, theta elutes later than expected, indicating that aggregation is potentially responsible for these problems. To address this issue, we recorded 1H-15N heteronuclear single quantum correlation (HSQC) spectra in water-alcohol mixed solvents and observed substantially improved dispersion and uniformity of peak intensities, facilitating a structural determination under these conditions. The structure of theta in 60/40 (vol/vol) water-methanol is similar to that of HOT but differs significantly from a previously reported theta structure. The new theta structure is expected to provide additional insight into its physiological role and its effect on the epsilon proofreading subunit.

PubMed: 16199579
DOI: 10.1128/JB.187.20.7081-7089.2005

Experimental method

SOLUTION NMR